One recent spring day, John Durban, a NOAA Fisheries marine mammal biologist, stood on the California coast and launched an unmanned aerial vehicle into the air. The hexacopter--so called because it has six helicopter-type rotors--zipped over the ocean and hovered above a gray whale mother and her calf. The pair was migrating north from their calving grounds off Baja California, Mexico, to their summer feeding grounds in the Arctic. NOAA Fisheries scientists have stood at this point of land each year for the past 22 years, binoculars in hand, to estimate the number of gray whale calves born each year. That's an important step in monitoring the ups and downs of the population. But scientists would like to understand more completely what causes those ups and downs, and this year, with the addition of the hexacopter, they hope to find out. As the hubcap-sized hexacopter hover...